2014-09-19

This review is based upon my impressions having immediately watched the film. I have since been informed that noted film critics differ from my views. But, this is my review so YMMV. And spoiler alert.

Eraserhead has multiple overlapping themes. The protagonist (Jack) coming to terms with new adulthood and fatherhood is covered elsewhere. A former student of mine says the film was about being uncomfortable in everything about yourself. To me there are two further themes:

1. Ending an obsession to clear mental space for the new. In this theme the baby represents a grotesque and under-formed idea on which Jack has begun a collaboration. While others abandon him, he is driven on by obsessive responsibility and social pressure. Once Jack has killed the baby then, metaphorically abandoning the bad idea, that new and better ideas come to him.

2. A catharsis for David Lynch as he comes to terms with what he then saw as selling out or compromising. In doing so he knows he will have access to greater resources with which to achieve greater ideas but that comes at a cost. This interpretation stems from how the symbols in the movie are interpreted.

The women in the film stand in for various genres. He sees lesser men flirting with the woman next door. What have they got that he hasn't? The smiley dream woman is the mainstream crappy film genre. She stomps on his ideas without mercy or guilt, always superficial and shiny but with her own flaws. Jack’s wife represents his early film-making circles: fickle, weak and without the endurance to achieve much of note.

The pencil factory is Jack’s job interview/school exams where he is being evaluated to see if he can produce the sharp but ultimately ephemeral popular movie. Like the pencil, these films are not intended to leave an indelible mark so that they can be replaced on a consumer cylce.

Once the baby is dead, Jack is rewarded with a burst of creative energy symbolised by pollen clouds releasing from plants in his room. The man in the planet then burns - representing Jack mastering his anxieties.

I don't pretend to read DL's mind or have access to any insider info: to my lack I know little about David Lynch. I don't begrudge any creative who does bread and butter work to pay for living and financing their more pure works.

2014-09-10

A few things have happened to my Ceph cluster. The AspireOne netbook was really not up to the job. It is fine for just a few OSD processes but anything more was caused slow-downs resulting in cluster thrash. Amalgamating thumb drives using LVM was helpful… until I wanted to run CephFS. I was time to add another node to the mix.

Read about earlier stories about the Ceph on USB thumb drive cluster here:

Adding another node to Ceph is trivial. This was an old, but much more powerful laptop in every way. I’ve moved the mon and mds functions onto this laptop so now the AspireOne only runs OSD processes. When I add another node then I’ll also run a mon process on the AspireOne so that there is an odd number for quorum building.

The new node uses faster and larger USB keys. These were 32GB – which was both the fastest and cheapest price per GB available at my local PBTech. The new node currently runs two of these sticks in an OSD process each.

I also moved the cluster away from XFS to BTRFS. This was trivial and involved zero cluster downtime. Yes: zero. First ensure the cluster is reasonably healthy, then drop the weight of the OSD using:

ceph osd reweight OSDID 0.1

. Actually I got bored waiting – the cluster was healthy and the pools all had size 3 with min_size 2… so I just stopped the OSD process and removed it from the ceph. Don’t do that on a live cluster, especially where pools have few replicas. But, this was just for testing. Then...

Then umount the backing storage and format it using BTRFS. Then I followed the instruction in my previous tutorial to add the storage back into Ceph. Wait for the cluster to heal before migrating another OSD from XFS to BTRFS.

The AspireOne node has three groups of 8GB keys, federated by USB hub. BTRFS is capable of spanning physical drives without LVM so I removed LVM once all groups had been migrated. Do read about the options for BTRFS stores because the choices matter. I went with RAID10 for the metadata and RAID0 for the data. RAID0 maybe gives better parallel IO performance because the extents are scattered among the drives but it does mean that all block devices in the FS effectively operate at the size of the smallest one. I can live with that.

Three BTRFS OSDs on the AspireOne is sometimes a bit much for that machine. Though, one cool thing about BTRFS was I extended a mounted BTRFS volume with a few more thumb drives, then restarted the osd process. Use

ceph osd crush reweight osd.X Y

to tell Ceph to reallocate space. That was instant storage expansion without downtime on the OSD long enough to trigger a recovery process. I did the whole process in less than ten minutes – and most of that was googling to find the correct BTRFS commands.

The cluster happily serves files to my desktop machine over CIFS. While it’s not a setup I’d recommend for production use it is kinda fun.